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Cell division and inheritance
- 1. Cell Division andInheritance
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- 3. Chromosomes- Threadlike structure,composed of DNA and a protein, that form in the nucleus when the cell begins to divide and that carry the genes which determine an individual's traits. They come in pairs. Every nucleus contains 23 pairs.
- 4. DNA-Complex chemical thatcontains the genetic information for Cell Growth, Division and Function. It controls- Hair Colour Eye Colour Height Face Shape Intellegence Blood Type PRETTY MUCH EVERYTHING!!
- 5. Genes- Short sectionsof DNA. Each gene has a specific purpose. It has the instructions for making a particular amino acid. The amino acids then join together to form proteins.
- 6. Asexual reproduction- Reproductionwithout the sexual union of male and female gametes. Mitosis- Cells divide into two. These two new calls contain the same DNA as the origional one and so are identical. Asexual reproduction is a 5 step program- 1. Take a parent cell. 2. The chromosomes make identical copies of themselves. 3. The chromosomes line up in the centre. 4. The copies serarate and move apart. 5. The cells split into two. Each cell has a copy of the origional cell's DNA. This happens again and again to produce lots of identical cells.
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- 8. Sexual reproduction- Reproductionby combining genetic information from two different sexes. Meiosis- Production of special cells called Gametes (Sperm and Egg) . This only happens in the reproductive organs. How does Meiosis work? The 23 chromosome pairs start copying themselves and double up. Then, sections of DNA get swapped between similar chromosome pairs. This swapping is where the genetic variation comes from. The call then divides into two and then them two both split again so there's four cells each containing 23 chromosomes. Each pair of chromosomes is split so that each sperm and egg cell only contain 23 single chromosomes. The male and female gametes then join together and their single chromosomes join up to make 23 pairs. This newly formed call contains a unique mis of chromoomes from each parent. This is called fertalisation.
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- 10. Comparison of Asexualand Sexual reproduction- Asexual Sexual Pro Con • High genetic variability. • Helps adaption. • "Speeds" up evolution. • Saves energy. • There's no need for 'Hanky Panky'. • Needs a lot of energy. • 'Hanky Panky' is time and resource consuming. • Low genetic variability. • Adaption to environment is difficult. • Decelerates evolution.
- 11. Inheritance- Genetic characteristicstransmitted from parent to offspring. Different forms of the same gene are called Alleles. For example- The gene for eye colour has an alele for blue eyes and an allele for brown eyes. Alleses are either Domninant or Recessive. In eye colour the brown allele is dominant to the blue allele. This means that if there were a blue and brown allele present the child would have brown eyes. Genetic diagrams- The rule is to use a capital letter to represent the dominant allele and a lower-case letter for the recessive.
- 12. Example of howa child can have blue eyes when both parents have brown- Brown is dominant so is represented by a 'B'. Blue is recessive so is represented by a 'b'. Bb Bb Bb Bb B Bb b bbBB
- 13. Sex chromosomes- Male-XY Female- XX The sex chromosomes pair determine whether you are male or female. Gametes only contain one sex chomosome. This means that all egg cells must contain an X where as sperm could either contain an X or Y chromosome. If the sperm cell contains the Y chromosome then the baby will have XY and be male and so if the sperm cell contains an X chromosome then the baby will have XX and be female.